Is it too late to take Valacyclic two days after a breakout of cold sores?

I forgot to apply medicine with the first sign of a cold sore yesterday . Today the sores are blistered and swollen. Topical ointment is not working as far as stopping the pain and itching . Tomorrow I see my doctor for a refill of valacyclovir ( she always seems to have me come in whenever I need a refill which takes longer). Anyway , I'm afraid the longer it takes the less effective valacyclovir will be. Has anyone had this delay before with taking valacyclovir, and what were the results ? Thanks .